Changes in microstructure and mechanical properties of the carbon fiber and their effects on C/SiC composites

The changes in microstructure and mechanical properties of the carbon fiber and their effects on C/SiC composites were studied. The H, N and O atoms escaped and the carbon content in the carbon fiber increased when the heat treatment temperature exceeds 1200 degrees C. Meanwhile, the growth of graphite crystallite leaded to stress concentration and reduced the tensile strength of carbon fiber to 2.98 GPa by 1200 degrees C heat treatment. The active atoms on the surface of the carbon fiber were reduced, thus weakening the bonding force between the carbon fiber and the pyrolytic carbon interface layer and improving the pullout mechanism of the carbon fiber. This result was also observed by synchrotron radiation X-ray computed tomography. The flexural strength of the C/ SiC composite increased from 300 MPa without treatment to 364 MPa after 1600 degrees C heat treatment.

Automated summary

This study investigates the changes in microstructure and mechanical properties of carbon fiber and their effects on C/SiC composites. The heat treatment temperature exceeding 1200 degrees C results in the escape of H, N, and O atoms and an increase in carbon content in the carbon fiber. Furthermore, the growth of graphite crystallite leads to stress concentration and reduces the tensile strength of carbon fiber. The reduced active atoms on the surface of carbon fiber weaken the bonding force between carbon fiber and the pyrolytic carbon interface layer, improving the pullout mechanism. After heat treatment at 1600 degrees C, the flexural strength of the C/SiC composite increases.